Method of and apparatus for burning pulverized fuel



March 19, 1929. R, Q w o s Y 1,706,360

METHOD OF AND APPARATUS FOR BURNING PULVERIZED FUEL Filed Jan. 27, 1921 2 Sheets-Sheet 1 March 19, 1929. Q NEWHOUSE 1,706,360

' METHOD OF AND APPARATUS FOR BURNING PULVERIZED FUEL Filed Jan'. 27, 1921 2 Sheets-Shea; 2

Patented Mar. 19, 1929.

a v 1,706,360 UNITED STATES PATENT OFFICE.

' BAY c. nnwnousn, or wauwa'rosa. Wisconsin, asslenon r aams-cnanunns manurnc'runme COMPANY, ,or DELAWARE.

MILWAUKEE, WISCONSIN, A CORPORATION OF METHOD OF AND APPARATUS I'OB BURNING PULVEBIZEID FUEL.

Application filed January 27, 192 1. Serial no. 440,401.

. This invention relates in general to improvements in the art of converting heat energy and relates more specificall to an improved method of and apparatus. or preventing the formation of slag coatings on adjacent structure, during combustion of pulverized fuels.

An object of the invention is to provide an improved method of converting heat energy. Another object is to provide a method of reventing accumulation of solidified slag uring combustion of fuels. A further ob ect is to provide a simple and eflicient process of utilizing pulverulent material such as powdered coal, for the purpose of heating an energy absorber such .as a boiler. Still another object is to provide simple and eflicient apparatus for burning pulverulent fuel and for preventing accumulation of slag during combustion of the material. An add 1- tional object is to provide apparatus wherein the heat of combustion resulting from the burning of fuel, may be utilized with mainmum efficiency.

It has recently been found commercially practical to utilize powdered coal for the purpose of heating steam generators and similar heat absorbers. The utilization of coal in pulverulent condition has a number'of ad vantages over the prior method of using mine run or coarse crushed coal, The pulverization of the coal facilitates handing thereof and also permits more eflicient and com lete combustion of the fuel. .The prohibitory.

high cost of the better gradesofjcoaland the inability in many'cases'to obtain a continuous and sufficient supply of such coalforfuel purposes, has in many instances made 1t necessary to utilizevcheaper gradesof fuel. Such use of the cheaper grades of fuel 1s found practicable when the coal is reduced to a powder and is injected into the combustion chamber in thispulverulent condition by means of a jet of air, it having been found possible by this manner of handlin to utilize low grade fuels which under or inary circumstances could not be used for heatlng' purposes. When using the coal in pulverulent condition; it has been found that if the gases of combustion are not diluted in some manner, the combustion is so violent as to create temperatures above the slagging temperature of the ingredients, especially of thes1hca, iron oxide and alumina, contained in the material.

With the production of such high temperatures, slag is usually deposited at the bottom of the combustion chamber and is also deposited as a coating upon the heat transferrmg portions of the heat absorber, thus producing an insulating coating which prevents eflicient transfer of the heat.

In order to prevent such objectionable accumulations o slag, it has heretofore'been proposed to mix the hot gases of combustion caving the combustion chamber, with relatlvely cold air introduced directly from the atmosphere. While this method has eliminated the accumulations of slag, it is objectionable in that the cold air thus introduced in relatively large quantities, must absorb sufficient heat from the gases of combustion resulting from the burning of the fuel, to raise the temperature a'considerable amount, thereby wasting considerable heat which might otherwise be available inthe heat absorber.

In order to eliminate undesirable accumulations of slag due to the creation of high temperatures in the combustion chamber without entailing the loss of heat as in the prior method, the present invention contemplates a method of introducing relativel hot gases which are mixedwith the gases 0 combustion to reduce their temperatures prior to delivery to, the heat absorber. Inthis manner, the

temperature of the gases of combustion may be readily reduced to a point below the slagging temperature of the fuel ingredients before thesegasesare brought in contact with the surfaces of the heat absorber, thereby preventing formation ofvslag in the combustion chamber and eliminating the prior obj ectionable -formation of heat insulating coatin upon the heat transferring surfaces of t e heat absorber. With the present invention, cooling ga having relatively high tempera from some which like reference characters designate the same or similar parts in theseveral views.

Fig. 1. is a diagrammatic central vertical section through a steam generating installation especially adapted to utilize powdered coal as fuel.

. Fig. 2 is a diagrammatic part sectional View through a combined powdered coal steam generating plant and rotary kiln installation.

Fig. 3 is a fragmentary top view, drawn to a reduced scale, of'the combined installation disclosed in Fig. 2.

Referring specifically to Fig. 1, the heat ing plant therein shown comprises in eneral a fire-proof housing forming a com ustion chamber 3 and a mixing chamber 30 in direct communication therewith, a heat ab sorbing device or steam boiler 2 located in proximity to the chambers 3, 30,, apparatus for delivering pulverulent fuel and air to the combustion chamber, and a stack 4 for delivering gases of combustion from the boiler. The" combustion chamber 3 is provided with suitable air inlet openings 10 and a fuel inlet conduit or pipe .9 preferably directed downwardly intothe chamber 3. The lower portion of the mixing chamber 30 is provided with a cleanout 11 for permitting removal of small quantities 'of materials which may accumulate during operation of the apparatus. The heat absorbing device or boiler 2 is preferaly located above and "to one side of the combustion chamber 3 and has a series of heat transferring tubes and baffles which compel the hot gases delivered to the boiler from the combustion and mixing chambers 3,. 30, to follow a circuitous path through the boiler. The gases leaving the spaces adjoining the tubes of the boiler 2, are delivered upwardly to the) stack 4. A return pipe 12 communicating with the stack 4 leads to the inlet opening of a blower 13 which delivers its discharge through a return injection pipe 14 into the lower portion of the mixing chamber 30. The fuel feeding apparatus which delivers a combustible mixture of air and pulverulent material to the combustion chamber 3 through the inlet pipe 9, comprises a fuel supply bin or hopper 5 having its lower end communicating with a feeder 6, and an air blower 8 having its discharge communicating with a nozzle 7 which is adapted to deliver a jet of air at high velocity past the discharge opening of the fuel 1 feeder 6 and into the fuel inlet pipe 9.

Referring specifically to Figs. 2 and 3, the heating plant-therein shown is generally similar to that disclosed in Fig. 1, comprising a fire-proof housing forming a combustion chamber 3 and a mixing chamber 30 in direct communication therewith, a heat absorbing device or steam boiler 2 located in proximity to the mixing chamber 30, and a stack 4 for delivering gases of combustion from the boiler. The combustion chamber 3 is provided with suitable air inlet openings 10 and I quantities of materials w iich may accumu-i late below the chambers 3, 30 during operation of the apparatus. The heat absorbing device or boiler 2 is preferably located above the mixing chamber 30 and has a series of heat transferring tubes and baflles which compel the hot gases delivered from the mixing chamber 30 to follow a circuitous path through the boiler. The gases leaving the boiler 2 are delivered upwardly to the stack 4. The fuel feeding apparatuswhich communicates with the combustion chamber 3 through the inlet pipe 9, comprises a'fuel supply bin or hopper 5 having its lower end communicating with the feeder 6,.an'd an air blower 8 having its discharge communicating with'a nozzle 7 which is adapted to delivera jet of air at high velocity through the pipe 9. Leadinglaterally into the combustion and mixing chambers 3, 30 is a series of conduits 21 communicating with a like series of rotary kilns 15. These kilns 15 are adapted to heat treat materials passed longitudinally therethrough and are provided with fuel feeding apparatus adapted to deliver a mixture of air and pulverized fuel to their lower extremities. Each of the kiln fuel feeding devices comprises a fuel supply bin or hopper 16 having its lower end communicating with a feeder 17, and an air blower20 having its discharge communicating with a nozzle 18. Each nozzle 18 is adapted todeliver'a jet of air at high velocitypast the discharge opening of the fuel feeder 17 and into the injection pipe 19 which leads to the lower end of the corresponding kiln 15. Within the kilns 15, the fuel thus injected is ignited and the heat of combustion is utilized to calcine solid material, passing longitudinally through the kiln. The hot gases of combustion from the kilns 15 are delivered through the conduits 21 and into the mixing 'chamber30, where they are intimately mixed with the relatively hot gases of combustion from chamber 3.

During normal operation of the apparatus disclosed in Fig. 1, the fuel feeder 6-and the air blower 8 are in operation, the blower producing a jet of air at thenozzle 7 which'mingles with the powdered coal and forces'the' combustible mixture of coal and air thus formed, downwardly into the combustion chamber 3 through the inlet pipe 9. In the combustion chamber 3 the combustible mixture thus injected, strikes the incandescent mass of burning mixture previously admitted, and is ignited and burned. The violent burning of the powdered fuel in the combustion chamber 3 in the presence of air, roduces temperatures which are considerab y above the slagging temperatures of the ingredients of the coal. The hot gases of combustion delivered from the combustion chamber 3 are drawn laterally and upwardly away from this chamber and toward the boiler 2, by' the draft induced in the stack 4., During this lateral and upward progress of the gases of 'mix with the hot gases of combustion leaving the combustion chamber 3 and reduce the tem peratures of these gases to a point below the slagging temperatures of the ingredients. The mixed ases thus produced are still of sufliciently high temperature to efficiently perform their heating function in the'boiler 2, and are passed through the spaces among the tubes of the boiler 2wherein their heat is transferred to the absorbing medium located within the tubes. Thespent gases of combustion are eventually delivered upwardly from theboiler 2 to the stack 4 wherein a part of the gases are withdrawn and returned to the combustion chamber through the pipes 12, 14 and blower 13, as hereinbefore described. The injection of the non-combust ible stack gases into the space below the combustion chamber 3 prevents the formation of slag below the chambers 3, 30 by reducing the temperatures of gases which 'ght otherwise strike the floor of these chambers, below the slagging' temperatures of the ingredients thereof. By cooling the gases of combustion delivered to the chamber 30 and by injecting the non-combustible stack gases and mixing them with the ases of combustion'prior to application of t e heat of combustion to the boiler 2, the formation of slag coatings on the boiler tubes is prevented. As-the gases of combustion passing through the stack 4- have relatively high temperature as compared with atmosphericair, the heat absorbed by the cooling gases from the gases of combustion, is considerably less than if atmospheric air were-used as a cooling agent, thereby pern'litting more eificient utilization of the heat of combustion in the boiler 2.

During normal operation of the apparatus disclosed in Figs. 2 and 3, the boiler 2iis being heated solely by the hot gases of combustion delivered from the kilns 15 through the discharge conduits 21. If, however, one or more ofit hese kilns 15'is thrown out of o eration, the gases of combustion delivered om the remaining kilns are not s'uflicient to supply the necessary heat to the boiler 2, whereupon the fuel feeder 6 and the air blower 8 we medium located within the tubes. gases of combustion 'fromthe chamber 3 and placed in operation. During suchoperation of the apparatus the blower'8 produces a jet of air at the nozzle 7 which mingleswith the powdered coal delivered from the feeder '6 and forces the combustible mixture of coal and air thus formed, downwardly into the combustion chamber 3. In the chamber 3 the combustible mixture is ignited and burned. The violent burning of the powdered fuel in the combustion chamber 3 in the presence of air, produces temperatures which'are considerably above the slagging temperatures of the ingredients. of the fuel The hot gases of combustion delivered downwardly from the combustion chamber 3 are diverted laterally and upwardly. around the dividing partition, by .the draft induced in the stack 4. During this lateral and upward progress of the gases of combustion, other .gassof combustion having relatively high temperature as compared with the atmospheric air, are deinjected below the combustion chamber 3 and into the mixing chamber 30. The kiln gases thus admitted are relatively cool as-compared with the gases of combustion generated in the chamber 3, being subsequentlydrawn through and u wardly from the mixing chamber 30 wherein they intimately mix ,with the gases the ingredients. The mixed gases thus produced are still of sufliciently high temperature to efliciently perform their heating function in the boiler 2, and are passed'throu-gh the spaces among the tubes of the boiler 2 where.

livered' from the remaining kilns 15, being i in their heat is transferred to the absorbing,

The spent the kilns 15 are delivered upwardly from the boiler 2 to the stack 4, The injection of the non-combustible kiln-gases in the space below the combustion chamber 3 prevents the accumulation of slag below the chambers 3,

30- by reducing the temperatures of gaseswhich might otherwise strike the 'floor' of these chambers, below the slagging temperatures of the ingredients thereof. Bycooling the gases of combustion delivered to the boiler 2 below the slagging temperature of the ingredients thereof, the formation of slag coatings on the boiler tubes is prevented. As the gases of combustion leaving the kilns 15 have relatively high temperature as compared with atmospheric air, the heat absorbed by the cooling gases from the gases of combustion generated in the chamber 3, is considerably less than if atmospheric air were used as a cooling agent thereby permitting more efficient utilization of the heat of combustion in the boiler 2. 1

It will thus be noted that'with the-use of either of the installations disclosed, accumulation of solidified slag is positively prevented apparatus for carrying on the present method,

it will be obvious that other apparatus may also be utilized to accomplish the desired rei been lowered-by abstraction of heat, and passsults. With the use of-the present method, the heating apparatus is automatically maintained in clean and eflicient condition thereby obtaining maximum efiiciency in the application of the heat of combustion.

It should be understood that it is not desired to limit the invention to the exact steps of the process and to the details of construc tion of the apparatus herein shown and described, for. obvious modifications within the scope of theappended claims may occur to persons skilled in the art.

It is claimed and desired to secure by Letters Patent 1. Themethod of generating and, utilizing heat, which consistsin injecting ash-containign fuel and air into a combustion chamber, burning the same in suspension, mixing with the hot products of combustion, products of combustion the temperature of which has ing'the. mixture through a heat transfer dev1ce.

2. The method of generating and utilizing heat, which consists in injecting ash-containing fuel and air into a combustion chamber, burning the same in suspension, mixing with the hot products of combustion products of combustion the temperature of w ich has been lowered by abstraction of heat, and passing the mixture through a. steam generator.

3. The method of generating and utilizing heat, which consists in injecting ash-containing fuel and air into a combustion chamber, burning the same in suspension, mixing with the hot products of combustion, products of combustion the temperature of which is below the fusing point of the ash, and passing the mixture through a heat transfer device.

4. The method of generating and utilizing heat, which consists in injecting ash-containing fuel and air into a combustion chamber, burnlng the same in suspenslon, mlxing with the hot products of combustion, products of fer device, and passing the mixture through said heat transfer device. y

'6. The method of generating and utilizing heat, which consists in injecting ash-containing fuel and air into a combustion chamber,

burning the same in suspension, mixing, with the hot products of combustion other products of combustion the temperature of which has been lowered by passage through a steam generator, and passing the mixture through said steam generator.

1 7. The method of generating and utilizing heat, which consists in introducing air and ash-containing fuel in a combustion zone. burning the same, subsequently mixing with the hot products of combustion other hot' products of combustion the temperature of which has been lowered by passage through a heat transfer device, andpassing the mixture through said heat transfer device.

8. The method of generating and utilizing heat, which consists in introducin air and ash-containing fuel in a combustion zone, burning the same, subsequently mixing with the hot products of combustion other hotproducts of combustion the temperature of which has been lowered by passage through a steam generator, and passing the mixture through said steam generator.

In testimony whereof, the signature of the inventor is afiixed hereto.

- RAY C. NEWHOUSE. 

